Such sensor arrangements are counted as belonging to the state of the art and comprise one or more sensors which are arranged in a housing manufactured of at least one injection molded part. Thereby, the sensor is either connected directly or via sensor electronics located in the housing, to at least one lead which is to be sealingly led through the housing.
Lead feed-throughs are counted as belonging to the state of the art and are differently elaborate but also differently tight, depending on the design. Whereas a sealed cable lead-through which can be released again is counted as belonging to the state of the art with larger housings for electrical apparatus, such a sealing is not suitable for sensor housings which as a rule are comparatively small.
With sensor housings, it is common to peripherally inject the leads together with a part of the housing with plastic and to thus create a sealed connection. The problem with these leads peripherally injected with plastic however is the fact that a firm bond or interconnection does not form between the lead and plastic, and a gap arises, in particular due to temperature fluctuations, via which gap moisture can penetrate into the housing, for example due to a capillary effect, by diffusion or in another manner. This is particularly problematic with small sensor housings, since even small quantities of moisture can be sufficient to damage the electronics located in the housing, or the sensor itself.
Although it is counted as belonging to the state of the art with sensor arrangements such as for example from EP 2 083 250 A1, to construct the housing in a multi-layered manner and to form at least one layer of a diffusion-tight plastic. It is also known to arrange a desiccant within the housing, in order to bind any penetrating moisture. Such desiccants such as silica gel or calcium chloride are counted as belonging to the state of the art, but however require a separate encasing, in order not to come into direct contact with the sensitive electronic components.
This problem is amplified with sensor arrangements with a comparatively small housing, with which the sensor itself is in contact with the fluid, as is the case for example with pressure sensors or differential pressure sensors or temperature sensors (EP 2 626 567 A1). Here too, the lead feed-through itself can be directly subjected to surrounding fluid, at least to a moist or humid environment.